Ice machines are widely used in restaurants and the like for producing ice, in the form of flakes, chips, cubes, etc. for use in beverages and for other uses relating to food and drink service. Ice machines are also used for making ice for retail sale in bags. Generally, these ice machines include an electrical refrigeration apparatus for freezing water supplied to the machine, a means for periodically removing, or "harvesting" ice from the freezing site and a cabinet or bin for storing the frozen ice until it is needed.
The design of the refrigeration section, and in particular the evaporator of the refrigerator, determines the shape of the resulting ice product. In accordance with customary usage in the industry, the term "ice cube" in this patent is intended to include ice particles of any shape, not just those which are geometrically perfect cubes. Thus, all types of squared or rounded-surfaced ice particles are still referred to as "ice cubes".
In a typical ice making apparatus, water is brought in contact with the evaporator tubes of the refrigeration system, or a surface being refrigerated by evaporator tubes, which causes chilling and freezing of the water. Over a period of time the ice layer grows as water continues to freeze to the evaporator surface. Often a secondary surface is included in the evaporator assembly and is shaped to work in conjunction with the evaporator tubes to control the shape of the ice cube as it grows. As freezing continues, the ice cube continues to grow to a particular shape which is dependent upon the geometry of the evaporator tube contact area and secondary surface at the freezing sites. This operation continues for an interval of time, typically fifteen or twenty minutes, until the size of the ice cube is adequate. At that point, the harvesting operation takes place to remove the cubes from the evaporator for storage or packaging.
The most common type of harvesting is hot gas harvesting, whereby high temperature gas exiting the compressor of the refrigeration system is diverted into all or part of the evaporator to heat it. The temperature in the refrigerant tubes rises and causes melting of a layer of previously formed ice in direct contact with the evaporator tubes. Because the ice will not release and drop off until all of its surface in contact with the evaporator surface and any secondary surfaces of the evaporator has melted, a considerable amount of heat must be applied to the evaporator tubes. A considerable amount of ice adjacent the evaporator tube will typically melt away in the time required for the melting and release of the cube at the furthest point of contact between the cube and the secondary surface. During the harvesting, a considerable amount of electrical power is consumed in operating the compressor and in melting ice previously made at the cost of consumed electrical energy.
Another type of harvesting involves flooding a top side of an evaporator structure with hot water, where ice has previously been formed on the bottom side of the evaporator at specific sites thereon by the spraying of water into contact with the evaporator. A considerable amount of energy is consumed in the heating of the water, typically to 150 degrees, for this method of harvesting.
Because of the increasing cost and scarcity of energy sources, the energy consumption of devices such as ice cube machines is coming under closer scrutiny, and there is a need for increasing efficiency, i.e. reducing energy consumption, in such devices.
Another problem encountered in prior art ice making machines involve the shape of the finished ice cube product. It has been found that ice cubes having large flat surfaces, such as rectangular or cube shaped ice cubes tend to become frozen together in large masses when stored in a bin or a retailing package. Curved ice cubes reduce the contact area with adjacent cubes and minimize the problem of freezing together during storage, but unfortunately the curved surface ice cubes produced by prior machines tend to have a cylindrical or pillow shape, with concave openings or surfaces which have a tendency of redirecting and reversing the direction of a stream of poured beverage, resulting in spraying or splattering.